Caesura: A pause, metrical or rhetorical, occurring somewhere in a line of poetry. The pause may or may not be typographically indicated.

King Lear example
Lear: And my poor fool is hanged. No, no, no life?
Why should a dog, a horse, a rat have life,
And thou no breath at all? Thou'lt come no more,
Never, never, never, never, never.
Pray you, undo this button. Thank you, sir.
Do you see this? Look on her! Look, her lips.
Look there, look there. [He dies]
Robert Frost example
There was never a sound beside the wood but one,
And that was my long scythe whispering to the ground.
What was it it whispered? I knew not well myself;
Perhaps it was something about the heat of the sun,
Something, perhaps, about the lack of sound—
(excerpt from Mowing)